Cocaine overdose among drug users is a common occurrence and contributes substantially to their mortality. There is no known "antidote" for cocaine toxicity that produces potentially lethal cardiac dysfunctions and seizures. Pharmacotherapies using new anti-epileptic drugs offer promise, as well as novel alternatives based on enzymes or antibodies. An antibody-based strategy for the treatment of cocaine overdose is presented. This proposal takes a new direction from our previously funded and successful work on cocaine vaccines and antibodies (DA08590) that emphasized therapy for addiction. The current plan is to develop monoclonal antibodies (mAbs), primarily in a whole IgG format, as an "antidote" for cocaine overdose intoxication. We will focus on 1) mAb technology based on the XenoMouse strain that produces fully human antibodies, 2) humanized mAbs derived from a murine mAb, 3) affinity-enhanced human and humanized mAbs, and 4) mAb protective effects against a lethal dose of cocaine in the mouse. Given our experience in the field, we have two immunogens in hand, GNC and GND, to derive human mAbs from the XenoMouse, and a murine mAb, GNC92H2, from which we have already constructed humanized mAbs. Furthermore, we used GNC92H2 as a proof-of-principle in a mouse model for cocaine overdose. The preliminary results indicated protective effects even when the mAb was administered after cocaine, as in a real-life scenario. In addition, we have also obtained a fully human antibody, GNCgzk, derived from the XenoMouse line that is greatly superior to GNC92H2 with regard to cocaine binding affinity. Further studies in the mouse model with improved mAbs such as GNCgzk will begin to provide essential information. Eventually, human or humanized mAbs might offer a safe, substance-specific therapeutic strategy, whereby the toxic and lethal consequences of cocaine overdose would be effectively avoided in the human condition.